function getQueryString(name) {
  var reg = new RegExp("(^|&)" + name + "=([^&]*)(&|$)", "i");
  var r = window.location.search.substr(1).match(reg); //获取url中"?"符后的字符串并正则匹配
  var context = "";
  if (r != null)
    context = decodeURIComponent(r[2]);
  reg = null;
  r = null;
  return context == null || context == "" || context == "undefined" ? "" : context;
}
